Forum Moderators: not2easy
I also agree it highly depends on quality not simply quantity. Decide what your goal is, then research your topic, craft well rounded content, then post that. Avoid what some bloggers do, posting a series of comments with no substance doesn't amount to much even if it is 10+ posts per day. No one will care.
Write content people want to read, then promote it. I wouldn't write less than one per week, in my opinion that's about as little "fresh" content as you want to average. Don't freak if you miss a week though, just average that amount.
To keep my site fairly fresh I add news once per day. They are not that extensive just a few lines from the latest press releases and announcements in the business. Takes me about 30-60 minutes a day and it's well worth it.